System.Security.Cryptography (mscorlib.dll)class
public class FromBase64Transform : ICryptoTransform, IDisposable {
// Public Constructors
   public FromBase64Transform(  );
   public FromBase64Transform(FromBase64TransformMode whitespaces);
// Public Instance Properties
   public virtual bool CanReuseTransform{get;
 // implements ICryptoTransform
   public bool CanTransformMultipleBlocks{get;
 // implements ICryptoTransform
   public int InputBlockSize{get;
 // implements ICryptoTransform
   public int OutputBlockSize{get;
 // implements ICryptoTransform
// Public Instance Methods
   public void Clear(  );
   public int TransformBlock(byte[  ] inputBuffer,  int inputOffset, int inputCount, 
       byte[  ] outputBuffer, int outputOffset);
// implements ICryptoTransform
   public byte[  ] TransformFinalBlock(byte[  ] inputBuffer, int inputOffset, int inputCount);
// implements ICryptoTransform
// Protected Instance Methods
   protected virtual void Dispose(bool disposing);
   protected override void Finalize(  );
 // overrides object

This implementation of the ICryptoTransform interface decodes Base64 data. This class is used in conjunction with the CryptoStream class.

    Part V: API Quick Reference